Indazolones, synthesis

Baiocchi Synthesis, properties and reactions of indazolones 78S633... 

Reaction of 3-Lithiomethyl-2-methyl-l-phenylpyrazolin-5-one with 6 A New General Method for the Synthesis of 1,2-Disubstituted Indazolones and Their Condensed Analogs (Type III, 3a Model)... 

This methodology with some variations has been utilized in the synthesis of numerous heterocyclic systems, such as heterocycle-fused quinolinone derivatives [391], l,4-benzodiazepin-2-ones [392], benzo-, naphtho- and heterocycle-fused pyrrolo[2,l-c][l,4]diazepines [393], quinolinone or pyrrolidinone derivatives [394], dibenzo[fl,c]phenanthridines [395], thiazolo-fused quinolinones [396], isoindolinone and isoquinolin-2-one derivatives [397], indoline derivatives [398], 5-aroyl-pyrrolidinones [399,400], indazolone derivatives [401,402], substituted indolizidinones [403], 1-arylpyrrolopyrazinones [404], stmcturally diverse... 

Indazoles have been used as the biosteres of indoles in drug discovery. In the synthesis of the nonsteroidal anti-inflammatory drug (NSAID) bendazac, benzylaniline was used as its starting material. Nitrosolation was accomplished using nitrous acid. The resulting A-nitroso intermediate was reduced with sodium thiosulfate to the corresponding hydrazine, which cyclized to the indazolone. Subsequent alkylation with methyl chloroacetate was followed by hydrolysis to deliver bendazac. 

Scheme 41 CuI/L-proline-catalyzed synthesis of 1-substituted indazolones...

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